Markers for detection of gastric cancer

ABSTRACT

Early detection of tumors is a major determinant of survival of patients suffering from tumors, including gastric tumors. Members of the GTM gene family can be differentially expressed in gastric tumor tissue, and thus can be used as markers for the detection of gastric and other types of cancer. The present invention provides for novel GTMs for the detection of tumors, including gastric tumors, and in particular human zymogen granule protein 16 (ZG16). The GTMs can be used in isolation or together with other known GTMs to provide for novel signatures to be used in the detection of tumors, including gastric tumors.

CLAIM OF PRIORITY

This application is a United States National Phase Application filedunder 35 U.S.C. §371 claiming priority to International Application No.PCT/NZ2010/000089, filed 14 May 2010, which claims priority to NewZealand Provisional Application No. 577,012, filed 15 May 2009. Each ofthese applications is herein fully incorporated by reference, as ifseparately so incorporated.

FIELD OF THE INVENTION

This invention relates to detection of cancer. Specifically, thisinvention relates to the use of genetic and/or protein markers fordetection of cancer, and more particularly to the use of genetic and/orprotein markers for detection of gastric cancer.

BACKGROUND

Survival of cancer patients is greatly enhanced when the cancer isdetected and treated early. In the case of gastric cancer, patientsdiagnosed with early stage disease have 5-year survival rates of 90%,compared to approximately 10% for patients diagnosed with advanceddisease. However, the vast majority of gastric cancer patients currentlypresent with advanced disease. Therefore, developments that lead toearly diagnosis of gastric cancer can lead to an improved prognosis forthe patients.

Identification of specific cancer-associated markers in biologicalsamples, including body fluids, for example, blood, urine, peritonealwashes and stool extracts can provide a valuable approach for the earlydiagnosis of cancer, leading to early treatment and improved prognosis.Specific cancer markers also can provide a means for monitoring diseaseprogression, enabling the efficacy of surgical, radiotherapeutic andchemotherapeutic treatments to be tracked. However, for a number ofmajor cancers, the available markers suffer from insufficientsensitivity and specificity. For example, the most frequently usedmarkers for gastric cancer, ca19-9, ca72-4 and carcino-embryonic antigen(CEA) detect only about 15-50% of gastric tumors of any stage, decliningto approximately 2-11% for early stage disease. Thus, there is a veryhigh frequency of false negative tests that can lead patients and healthcare practitioners to believe that no disease exists, whereas in fact,the patient may have severe cancer that needs immediate attention.Moreover, these markers can give false positive signals in up to ⅓ ofindividuals affected by benign gastric disease.

SUMMARY OF THE INVENTION

Aspects of this invention provide methods, compositions and devices thatcan provide for detection of early stage cancer, and decrease thefrequency of false positives and false negative test results.

In certain embodiments, molecular analyses can be used to identify genesthat are highly expressed in gastric tumor tissue, but not necessarilyover-expressed compared to non-malignant gastric tissue. Such analysesinclude microarray and quantitative polymerase chain reaction (qPCR)methods. Cancer genes, RNAs and proteins encoded by those genes areherein termed gastric tumor markers (GTM). It is to be understood thatthe term GTM does not require that the marker be specific only forgastric tumors. Rather, expression of GTM can be increased in othertypes of tumors, including malignant or non-malignant tumors, includinggastric, bladder, colorectal, pancreatic, ovarian, skin (e.g.,melanomas), liver, esophageal, endometrial and brain cancers, amongothers. It should be understood, however that the term GTM does notinclude the prior art markers, such as CA19-9, CA72-4, pepsinogen andCEA, or any other markers that have been previously identified as beingindicative of gastric tumors. Some GTM are secreted or escape fromtumors at sufficient levels to be diagnostic of gastric cancer with ahigh degree of reliability, and in other cases, measurement of two ormore GTM can provide reliable diagnosis of gastric cancer.

Proteins that are secreted by or cleaved from the cell, either alone orin combination with each other, have utility as serum or body fluidmarkers for the diagnosis of gastric cancer or as markers for monitoringthe progression of established disease. Detection of protein markers canbe carried out using methods known in the art, and include the use ofmonoclonal antibodies, polyclonal antisera and the like.

Specifically the present invention provides for a method for detectinggastric cancer, comprising:

-   -   (i) providing a biological sample; and    -   (ii) detecting the levels of human zymogen granule protein 16        (“ZG16”) in said sample.

In one aspect, and over expression of ZG16 in a patient is indicative ofthe patient having gastric cancer.

The further GTM family member according to the present invention may beselected from the group consisting of mucin 5AC (“MUC5AC”), or mucin 17(“MUC17”). The method may involve the detection of ZG16 and MUC5AC, ZG16and MUC17, or Z316 and MUC5AC and MUC17.

The further GTM family member may also comprise one or more further GTMfamily member, for example anyone of MUC5AC, MUC17, ZG16,carboxypeptidase N, polypeptide 2, 83 kDa chain (CPN2), matrixmetalloproteinase 12 (MMP12), inhibin (“INHBA”), insulin-like growthfactor 7 (“IGFBP7”), gamma-glutamyl hydrolase (“GGH”), leucine prolineenriched proteoglycan (“LEPRE1”), cystatin S (“CST4”), secretedfrizzled-related protein 4 (“SFRP4”), asporin (“ASPN”), cell growthregulator with EF hand domain 1 (“CGREF1”), kallikrein 10 (KLK10),tissue inhibitor of metalloproteinase 1 (“TIMP1”), secreted acidiccysteine-rich protein (“SPARC”), transforming growth factor, 13-induced(“TGFBI”), EGF-containing fibulin-like extracellular matrix protein 2(“EFEMP2”), lumican (“LUM”), stannin (“SNN”), secreted phosphoprotein 1(“SPP1”), chondroitin sulfate proteoglycan 2 (“CSPG2”),N-acylsphingosine amidohydrolase (“ASAH1”), serine protease 11(“PRSS11”), secreted frizzled-related protein 2 (“SFRP2”), phospholipaseA2, group XIIB (“PLA2G12B”), spondin 2, extracellular matrix protein(“SPON2”), olfactomedin 1 (“OLFM1”), thrombospondin repeat containing 1(“TSRC1”), thrombospondin 2 (“THBS2”), adlican, cystatin SA (“CST2”),cystatin SN (“CST1”), lysyl oxidase-like enzyme 2 (“LOXL2”),thyroglobulin (“TG”), transforming growth factor beta1 (“TGFB1”), serineor cysteine proteinase inhibitor Clade H, member 1 (“SERPINH1”), serineor cysteine proteinase inhibitor Clade B, member 5 (“SERPINB5”), matrixmetalloproteinase 2 (“MMP2”), proprotein convertase subtilisin/kexintype 5 (“PCSK5”), hyaluronan glycoprotein link protein 4 (“HAPLN4”),CA19-9, CA72-4, pepsinogen, CEA, MUC5AC and MUC17.

One example of a combination GTM markers according to the presentinvention is MUC5AC, MUC17, ZG16, cystatin SN, serpinH1 and serpinB5

Any suitable method for detecting the level of the GTM can be used, andmay include detecting the levels of a GTM mRNA, GTM cDNA, using anoligonucleotide complementary to at least a portion of said GTM cDNA,using qRT-PCR method using a forward primer and a reverse primer,detecting the levels of a GTM protein, detecting the levels of a GTMpeptide, for example using an antibody directed against said GTM. Anysuitable antibody can be used, and may be a monoclonal antibody or apolyclonal antiserum. The method may be carried out using asandwich-type immunoassay method, or using an antibody chip.

The present invention also provides for a device for detecting a GTM,comprising: a substrate having a GTM capture reagent thereon; and adetector associated with said substrate, said detector capable ofdetecting a GTM associated with said capture reagent.

The GTM capture reagent may be an oligonucleotide or an antibodyspecific for either a GTM oligonucleotide, a GTM protein or a GTMpeptide.

A further aspect of the present invention is a kit for detecting cancer,comprising:

a substrate having a GTM capture reagent thereon;

a means for visualizing a complex of said GTM capture agent and a GTM;reagents; and instructions for use, wherein said GTM comprises humanzymogen granule protein 16 (“ZG16”).

The GTM capture reagent is a GTM-specific oligonucleotide or aGTM-specific antibody selective for a GTM oligonucleotide, a GTM proteinor a GTM peptide.

The present invention also provides for a method for detecting gastriccancer, comprising the steps of:

providing a test sample from a patient at risk of having gastric cancer;measuring the presence of a GTM protein in said test sample; and

comparing the amount of GTM present in said test sample with a valueobtained from a control sample from a subject not having gastric cancer,wherein said GTM comprises human zymogen granule protein 16 (“ZG16”).

In a yet further aspect the invention provides for a method forscreening for gastric cancer, comprising the steps of: providing a testsample from a test subject;

measuring the presence of a GTM in said test sample; and

comparing the amount of GTM present in said test sample with a valueobtained from a control sample from a subject not having gastric cancer,wherein said GTM comprises human zymogen granule protein 16 (“ZG16”).

The GTM may be a GTM protein or peptide, or an oligonucleotide specificfor a GTM. The oligonucleotide may be DNA or RNA.

According the method, the step of measuring may use an ELISA assay.

The test sample may be obtained from plasma, tissue, urine, gastricfluid, serum and stool.

BRIEF DESCRIPTION OF THE FIGURES

This invention is described with reference to specific embodimentsthereof and with reference to the figures, in which:

FIG. 1 depicts a table of microarray analysis showing genes with highrelative expression in tumor tissue. Signal intensity for each gene inboth tumor tissue and non-malignant tissue was ranked. The table showsGTMs with a higher ranking than the existing gastric cancer marker CEA(encoded by the gene CEACAM5).

FIG. 2 depicts a table showing the characteristics of serum samples usedin antibody array analysis.

FIG. 3 depicts histograms showing the distribution of tumor andnonmalignant samples according to their level of expression of (a) ZG16and (b) MUC17. The level of expression of the two genes was obtainedusing RT-qPCR.

FIG. 4 depicts boxplots showing the detection of (a) MUC17 and (b) ZG16in the serum of gastric cancer patients and controls using antibodyarrays and RCA detection.

DETAILED DESCRIPTION Definitions

Before describing embodiments of the invention in detail, it will beuseful to provide some definitions of terms as used herein.

The term “GTM” or “gastric tumor marker” or “GTM family member” means agene, gene fragment, RNA, RNA fragment, protein or protein fragmentrelated or other identifying molecule associated with gastric cancer.The GTMs disclosed as part of the present invention do not includemolecules that are known in the prior art to be associated with gastriccancer, e.g. CA19-9, CA72-4, pepsinogen and CEA. However, the markers ofthe present invention can be used in novel and inventive combinationswith previously disclosed GTMs.

The term “marker” refers to a molecule that is associated quantitativelyor qualitatively with the presence of a biological phenomenon. Examplesof “markers” include a polynucleotide, such as a gene or gene fragment,RNA or RNA fragment; or a gene product, including a polypeptide such asa peptide, oligopeptide, protein, or protein fragment; or any relatedmetabolites, by products, or any other identifying molecules, such asantibodies or antibody fragments, whether related directly or indirectlyto a mechanism underlying the phenomenon. The markers of the inventioninclude the nucleotide sequences (e.g., GenBank sequences) as disclosedherein, in particular, the full-length sequences, any coding sequences,any fragments, or any complements thereof, and any measurable markerthereof as defined above.

As used herein “antibodies” and like terms refer to immunoglobulinmolecules and immunologically active portions of immunoglobulin (Ig)molecules, i.e., molecules that contain an antigen binding site thatspecifically binds (immunoreacts with) an antigen. These include, butare not limited to, polyclonal, monoclonal, chimeric, single chain, Fc,Fab, Fab′, and Fab₂ fragments, and a Fab expression library. Antibodymolecules relate to any of the classes IgG, IgM, IgA, IgE, and IgD,which differ from one another by the nature of heavy chain present inthe molecule. These include subclasses as well, such as IgGI, IgG2, andothers. The light chain may be a kappa chain or a lambda chain.Reference herein to antibodies includes a reference to all classes,subclasses, and types. Also included are chimeric antibodies, forexample, monoclonal antibodies or fragments thereof that are specific tomore than one source, e.g., a mouse or human sequence. Further includedare camelid antibodies, shark antibodies or nanobodies.

The terms “cancer” and “cancerous” refer to or describe thephysiological condition in mammals that is typically characterized byabnormal or unregulated cell growth. Cancer and cancer pathology can beassociated, for example, with metastasis, interference with the normalfunctioning of neighbouring cells, release of cytokines or othersecretory products at abnormal levels, suppression or aggravation ofinflammatory or immunological response, neoplasia, premalignancy,malignancy, invasion of surrounding or distant tissues or organs, suchas lymph nodes, etc. Specifically included are melanomas.

The term “tumour” refers to all neoplastic cell growth andproliferation, whether malignant or benign, and all pre-cancerous andcancerous cells and tissues.

The term “gastric cancer” refers to a tumor originating in the stomach.These tumors are able to metastasize to any organ.

The terms “differentially expressed,” “differential expression,” andlike phrases, refer to a gene marker whose expression is activated to ahigher or lower level in a subject (e.g., test sample) having acondition, specifically cancer, such as melanoma, relative to itsexpression in a control subject (e.g., reference sample). The terms alsoinclude markers whose expression is activated to a higher or lower levelat different stages of the same condition; in diseases with a good orpoor prognosis; or in cells with higher or lower levels ofproliferation. A differentially expressed marker may be either activatedor inhibited at the polynucleotide level or polypeptide level, or may besubject to alternative splicing to result in a different polypeptideproduct. Such differences may be evidenced by a change in mRNA levels,surface expression, secretion or other partitioning of a polypeptide,for example.

Differential expression may include a comparison of expression betweentwo or more markers (e.g., genes or their gene products); or acomparison of the ratios of the expression between two or more markers(e.g., genes or their gene products); or a comparison of two differentlyprocessed products (e.g., transcripts or polypeptides) of the samemarker, which differ between normal subjects and diseased subjects; orbetween various stages of the same disease; or between diseases having agood or poor prognosis; or between cells with higher and lower levels ofproliferation; or between normal tissue and diseased tissue,specifically cancer, or melanoma. Differential expression includes bothquantitative, as well as qualitative, differences in the temporal orcellular expression pattern in a gene or its expression products among,for example, normal and diseased cells, or among cells which haveundergone different disease events or disease stages, or cells withdifferent levels of proliferation.

The term “expression” includes production of polynucleotides andpolypeptides, in particular, the production of RNA (e.g., mRNA) from agene or portion of a gene, and includes the production of a polypeptideencoded by an RNA or gene or portion of a gene, and the appearance of adetectable material associated with expression. For example, theformation of a complex, for example, from a polypeptide-polypeptideinteraction, polypeptide-nucleotide interaction, or the like, isincluded within the scope of the term “expression”. Another example isthe binding of a binding ligand, such as a hybridization probe orantibody, to a gene or other polynucleotide or oligonucleotide, apolypeptide or a protein fragment, and the visualization of the bindingligand. Thus, the intensity of a spot on a microarray, on ahybridization blot such as a Northern blot, or on an immunoblot such asa Western blot, or on a bead array, or by PCR analysis, is includedwithin the term “expression” of the underlying biological molecule.

The terms “expression threshold,” and “defined expression threshold” areused interchangeably and refer to the level of a marker in questionoutside which the polynucleotide or polypeptide serves as a predictivemarker for patient survival. The threshold will be dependent on thepredictive model established are derived experimentally from clinicalstudies such as those described in the Examples below. Depending on theprediction model used, the expression threshold may be set to achievemaximum sensitivity, or for maximum specificity; or for minimum error(maximum classification rate). For example a higher threshold may be setto achieve minimum errors, but this may result in a lower sensitivity.Therefore, for any given predictive model, clinical studies will be usedto set an expression threshold that generally achieves the highestsensitivity while having a minimal error rate. The determination of theexpression threshold for any situation is well within the knowledge ofthose skilled in the art.

The term “sensitivity” means the proportion of individuals with thedisease who test (by the model) positive. Thus, increased sensitivitymeans fewer false negative test results.

The term “specificity” means the proportion of individuals without thedisease who test (by the model) negative. Thus, increased specificitymeans fewer false positive test results.

The term “microarray” refers to an ordered or unordered arrangement ofcapture agents, preferably polynucleotides (e.g., probes) orpolypeptides on a substrate. See, e.g., Microarray Analysis, M. Schena,John Wiley & Sons, 2002; Microarray Biochip Technology, M. Schena, ed.,Eaton Publishing, 2000; Guide to Analysis of DNA Microarray. Data, S.Knudsen, John Wiley & Sons, 2004; and Protein Microarray Technology, D.Kambhampati, ed., John Wiley & Sons, 2004.

The term “oligonucleotide” refers to a polynucleotide, typically a probeor primer, including, without limitation, single-strandeddeoxyribonucleotides, single- or double-stranded ribonucleotides, RNA:DNA hybrids, and double-stranded DNAs. Oligonucleotides, such assingle-stranded DNA probe oligonucleotides, are often synthesized bychemical methods, for example using automated oligonucleotidesynthesizers that are commercially available, or by a variety of othermethods, including in vitro expression systems, recombinant techniques,and expression in cells and organisms.

The term “overexpression” or “overexpressed” refers to an expressionlevel of a gene or marker in a patient that is above that seen in normaltissue. Expression may be considered to be overexpressed if it is 1.2,1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or greater then 2 times theexpression in normal tissue.

The term “polynucleotide,” when used in the singular or plural,generally refers to any polyribonucleotide or polydeoxribonucleotide,which may be unmodified RNA or DNA or modified RNA or DNA. Thisincludes, without limitation, single- and double-stranded DNA, DNAincluding single- and double-stranded regions, single- anddouble-stranded RNA, and RNA including single- and double-strandedregions, hybrid molecules comprising DNA and RNA that may besingle-stranded or, more typically, double-stranded or include single-and double-stranded regions. Also included are triple-stranded regionscomprising RNA or DNA or both RNA and DNA. Specifically included aremRNAs, cDNAs, and genomic DNAs, and any fragments thereof. The termincludes DNAs and RNAs that contain one or more modified bases, such astritiated bases, or unusual bases, such as inosine. The polynucleotidesof the invention can encompass coding or non-coding sequences, or senseor antisense sequences. It will be understood that each reference to a“polynucleotide” or like term, herein, will include the full-lengthsequences as well as any fragments, derivatives, or variants thereof.

“Polypeptide,” as used herein, refers to an oligopeptide, peptide, orprotein sequence, or fragment thereof, and to naturally occurring,recombinant, synthetic, or semi-synthetic molecules. Where “polypeptide”is recited herein to refer to an amino acid sequence of a naturallyoccurring protein molecule, “polypeptide” and like terms, are not meantto limit the amino acid sequence to the complete, native amino acidsequence for the full-length molecule. It will be understood that eachreference to a “polypeptide” or like term, herein, will include thefull-length sequence, as well as any fragments, derivatives, or variantsthereof.

The term “qPCR” or “QPCR” refers to quantitative polymerase chainreaction as described, for example, in PCR Technique: Quantitative PCR,J. W. Larrick, ed., Eaton Publishing, 1997, and A-Z of Quantitative PCR,S. Bustin, ed., IUL Press, 2004.

The term RCA is an abbreviation for rolling circle amplification. RCA isa technique which involves the repeated copying of a circular templateto amplify a signal, in a linear manner.

“Stringency” of hybridization reactions is readily determinable by oneof ordinary skill in the art, and generally is an empirical calculationdependent upon probe length, washing temperature, and saltconcentration. In general, longer probes require higher temperatures forproper annealing, while shorter probes need lower temperatures.Hybridization generally depends on the ability of denatured DNA toreanneal when complementary strands are present in an environment belowtheir melting temperature. The higher the degree of desired homologybetween the probe and hybridisable sequence, the higher the relativetemperature which can be used. As a result, it follows that higherrelative temperatures would tend to make the reaction conditions morestringent, while lower temperatures less so. Additional details andexplanation of stringency of hybridization reactions, are found e.g., inAusubel et al., Current Protocols in Molecular Biology, WileyInterscience Publishers, (1995).

“Stringent conditions” or “high stringency conditions”, as definedherein, typically: (1) employ low ionic strength and high temperaturefor washing, for example 0.015 M sodium chloride/0.0015 M sodiumcitrate/0.1% sodium dodecyl sulfate at 50° C.; (2) employ a denaturingagent during hybridization, such as formamide, for example, 50% (v/v)formamide with 0.1% bovine serum albumin/0.1% Fico11/0.1%polyvinylpyrrolidone/50 mM sodium phosphate, buffer at pH 6.5 with 750mM sodium chloride, 75 mM sodium citrate at 42° C.; or (3) employ 50%formamide, 5×SSC (0.75 M NaCl, 0.075 M sodium citrate), 50 mM sodiumphosphate (pH 6.8), 0.1% sodium pyrophosphate, 5×, Denhardt's solution,sonicated salmon sperm DNA (50 ug/ml), 0.1% SDS, and 10% dextran sulfateat 42° C., with washes at 42° C. in 0.2×SSC (sodium chloride/sodiumcitrate) and 50% formamide at 55° C., followed by a high-stringency washcomprising 0.1×SSC containing EDTA at 55° C.

“Moderately stringent conditions” may be identified as described bySambrook et al., Molecular Cloning: A Laboratory Manual, New York: ColdSpring Harbor Press, 1989, and include the use of washing solution andhybridization conditions (e.g., temperature, ionic strength, and % SDS)less stringent that those described above. An example of moderatelystringent conditions is overnight incubation at 37° C. in a solutioncomprising: 20% formamide, 5×SSC (150 mM NaCl, 15 mM trisodium citrate),50 mM sodium phosphate (pH 7.6), 5×Denhardt's solution, 10% dextransulfate, and 20 mg/ml denatured sheared salmon sperm DNA, followed bywashing the filters in 1×SSC at about 37-50° C. The skilled artisan willrecognize how to adjust the temperature, ionic strength, etc. asnecessary to accommodate factors such as probe length and the like.

The term “MUC5AC” means mucin 5AC (Seq ID Nos 1 and 4), and includes themarker MUC5AC, including a polynucleotide, such as a gene or genefragment, RNA or RNA fragment; or a gene product, including apolypeptide such as a peptide, oligopeptide, protein, or proteinfragment; or any related metabolites, by products, or any otheridentifying molecules, such as antibodies or antibody fragments

The term “MUC17” means human mucin 17, cell surface associated (Seq IDNos 2 and 5), and includes the marker MUC17, including a polynucleotide,such as a gene or gene fragment, RNA or RNA fragment; or a gene product,including a polypeptide such as a peptide, oligopeptide, protein, orprotein fragment; or any related metabolites, by products, or any otheridentifying molecules, such as antibodies or antibody fragments.

The term “ZG16” means human zymogen granule protein 16 (Seq ID Nos 3 and6), and includes the marker ZG16, including a polynucleotide, such as agene or gene fragment, RNA or RNA fragment; or a gene product, includinga polypeptide such as a peptide, oligopeptide, protein, or proteinfragment; or any related metabolites, by products,

or any other identifying molecules, such as antibodies or antibodyfragments.

The practice of the present invention will employ, unless otherwiseindicated, conventional techniques of molecular biology (includingrecombinant techniques), microbiology, cell biology, and biochemistry,which are within the skill of the art. Such techniques are explainedfully in the literature, such as, Molecular Cloning: A LaboratoryManual, 2nd edition, Sambrook et al., 1989; Oligonucleotide Synthesis, MJ Gait, ed., 1984; Animal Cell Culture, R. I. Freshney, ed., 1987;Methods in Enzymology, Academic Press, Inc.; Handbook of ExperimentalImmunology, 4th edition, D. M. Weir & CC. Blackwell, eds., BlackwellScience Inc., 1987; Gene Transfer Vectors for Mammalian Cells, J. M.Miller & M. P. Cabs, eds., 1987; Current Protocols in Molecular Biology,P. M. Ausubel et al., eds., 1987; and PCR: The Polymerase ChainReaction, Mullis et al., eds., 1994.

It is to be understood that the above terms may refer to protein, DNAsequence and/or RNA sequence. It is also to be understood that the aboveterms also refer to non-human proteins, DNA and/or RNA having homologoussequences as depicted herein.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Typically, tumor markers are differentially expressed between tumortissue and corresponding non-malignant tissue. This provides a means todistinguish between patients with and without cancer. However, it isprobable that the anatomical structure and physiological characteristicsof tumor tissues will lead to differences in the accumulation of markersin serum and other biological fluids even when those markers aren'tover-expressed in tumor tissue. In particular, the abnormal polarity oftumor cells, the leaky vasculature and the high interstitial pressure oftumor tissue would be predicted to favour the efflux of specific markersout of tumor tissue compared to non-malignant tissue. Consequently, itis hypothesized that secreted proteins that are expressed at very highlevels in gastric tumour tissue, but not necessarily over-expressedcompared to non-malignant gastric tissue, would constitute usefulgastric cancer markers.

Using a combination of microarray analysis and quantitative polymerasechain reaction (qPCR), novel markers for the detection of gastric cancerhave been identified. This novel gastric tumor marker (GTM), providefurther tools in the early detection of gastric cancer. Specifically,the invention comprises the novel GTMs: MUC5AC (Seq ID Nos 1 and 4),MUC17 (Seq ID Nos 2 and 5), and ZG16 (Seq ID Nos 3 and 6).

The novel GTMs can be used in isolation, or alternatively they can becombined together as signature (comprising two or more GTMs). Asignature according to the present invention includes at least one ofMUC5AC, MUG 17, and ZG16, and at least one further GTM, which can eitherbe a GTM according to the present invention, or any other GTM, includingknown GTMs.

Known GTMs suitable for use in combination with the presently disclosedGTMs include carboxypeptidase N, polypeptide 2, 83 kDa chain (CPN2),matrix metalloproteinase 12 (MMP12), inhibin (“INHBA”), insulin-likegrowth factor 7 (“IGFBP7”), gamma-glutamyl hydrolase (“GGH”), leucineproline-enriched proteoglycan (“LEPREI”), cystatin S (“CST4”), secretedfrizzled-related protein 4 (“SFRP4”), asporin (“ASPN”), cell growthregulator with EF hand domain 1 (“CGREF1”), kallikrein 10 (KLK10),tissue inhibitor of metalloproteinase 1 (“TIMP1”), secreted acidiccysteine-rich protein (“SPARC”), transforming growth factor, 13-induced(“TGFBI”), EGF-containing fibulin-like extracellular matrix protein 2(“EFEMP2”), lumican (“LUM”), stannin (“SNN”), secreted phosphoprotein 1(“SPP1”), chondroitin sulfate proteoglycan 2 (“CSPG2”),N-acylsphingosine amidohydrolase (“ASAH1”), serine protease 11(“PRSS11”), secreted frizzled-related protein 2 (“SFRP2”), phospholipaseA2, group XIIB (“PLA2G12B”), spondin 2, extracellular matrix protein(“SPON2”), olfactomedin 1 (“OLFM1”), thrombospondin repeat containing 1(“TSRC1”), thrombospondin 2 (“THBS2”), adlican, cystatin SA (“CST2”),cystatin SN (“CSTI”), lysyl oxidase-like enzyme 2 (“LOXL2”),thyroglobulin (“TG”), transforming growth factor beta 1 (“TGFB1”),serine or cysteine proteinase inhibitor Clade H, member 1 (“SERPINH1”),serine or cysteine proteinase inhibitor Clade B, member 5 (“SERPINB5”),matrix metalloproteinase 2 (“MMP2”), proprotein convertasesubtilisin/kexin type 5 (“PCSK5”), hyaluronan glycoprotein link protein4 (“HAPLN4”), CA19-9, CA72-4, pepsinogen and CEA, or any other markersthat have been previously identified as being indicative of gastrictumors.

By the term “reliability” we include the low incidence of falsepositives and/or false negatives. Thus, with higher reliability of amarker, fewer false positives and/or false negatives are associated withdiagnoses made using that marker. Therefore, in certain embodiments,markers are provided that permit detection of gastric cancer withreliability greater than the reliability of prior art markers of about50%. In other embodiments, markers are provided that have reliabilitygreater than about 70%; in other embodiments, greater than about 73%, instill other embodiments, greater than about 80%, in yet furtherembodiments, greater than about 90%, in still others, greater than about95%, in yet further embodiments greater than about 98%, and in certainembodiments, about 100% reliability.

General Approaches to Cancer Detection

General methodologies for determining expression levels are outlinedbelow, although it will be appreciated that any method for determiningexpression levels would be suitable.

Quantitative PCR (VCR)

Quantitative PCR (qPCR) can be carried out on tumour samples, on serumand plasma using GTM specific primers and probes. In controlledreactions, the amount of product formed in a PCR reaction (Sambrook, J.,E Fritsch, E. and T Maniatis, Molecular Cloning: A Laboratory Manual3^(rd). Cold Spring Harbor Laboratory Press: Cold Spring Harbor (2001))correlates with the amount of starting template. Quantification of thePCR product can be carried out by stopping the PCR reaction when it isin log phase, before reagents become limiting. The PCR products are thenelectrophoresed in agarose or polyacrylamide gels, stained with ethidiumbromide or a comparable DNA stain, and the intensity of stainingmeasured by densitometry. Alternatively, the progression of a PCRreaction can be measured using PCR machines such as the AppliedBiosystems' Prism 7000 or the Roche LightCycler which measure productaccumulation in real-time. Real-time PCR measures either thefluorescence of DNA intercalating dyes such as Sybr Green into thesynthesized PCR product, or the fluorescence released by a reportermolecule when cleaved from a quencher molecule; the reporter andquencher molecules are incorporated into an oligonucleotide probe whichhybridizes to the target DNA molecule following DNA strand extensionfrom the primer oligonucleotides. The oligonucleotide probe is displacedand degraded by the enzymatic action of the Taq polymerase in the nextPCR cycle, releasing the reporter from the quencher molecule. In onevariation, known as Scorpion®, the probe is covalently linked to theprimer.

Reverse Transcription PCR (RT-PCR)

RT-PCR can be used to compare RNA levels in different samplepopulations, in normal and tumour tissues, with or without drugtreatment, to characterize patterns of expression, to discriminatebetween closely related RNAs, and to analyze RNA structure.

For RT-PCR, the first step is the isolation of RNA from a target sample.The starting material is typically total RNA isolated from human tumoursor tumour cell lines, and corresponding normal tissues or cell lines,respectively. RNA can be isolated from a variety of samples, such astumour samples from breast, lung, colon (e.g., large bowel or smallbowel), colorectal, gastric, esophageal, anal, rectal, prostate, brain,liver, kidney, pancreas, spleen, thymus, testis, ovary, uterus, bladderetc., tissues, from primary tumours, or tumour cell lines, and frompooled samples from healthy donors. If the source of RNA is a tumour,RNA can be extracted, for example, from frozen or archivedparaffin-embedded and fixed (e.g., formalin-fixed) tissue samples.

The first step in gene expression profiling by RT-PCR is the reversetranscription of the RNA template into cDNA, followed by its exponentialamplification in a PCR reaction. The two most commonly used reversetranscriptases are avian myeloblastosis virus reverse transcriptase(AMV-RT) and Moloney murine leukaemia virus reverse transcriptase(MMLV-RT). The reverse transcription step is typically primed usingspecific primers, random hexamers, or oligo-dT primers, depending on thecircumstances and the goal of expression profiling. For example,extracted RNA can be reverse-transcribed using a GeneAmp RNA PCR kit(Perkin Elmer, Calif., USA), following the manufacturer's instructions.The derived cDNA can then be used as a template in the subsequent PCRreaction.

Although the PCR step can use a variety of thermostable DNA-dependentDNA polymerases, it typically employs the Taq DNA polymerase, which hasa 5′-3′ nuclease activity but lacks a 3-5′ proofreading endonucleaseactivity. Thus, TaqMan gPCR typically utilizes the 5′ nuclease activityof Taq or Tth polymerase to hydrolyze a hybridization probe bound to itstarget amplicon, but any enzyme with equivalent 5′ nuclease activity canbe used.

Two oligonucleotide primers are used to generate an amplicon typical ofa PCR reaction. A third oligonucleotide, or probe, is designed to detectnucleotide sequence located between the two PCR primers. The probe isnon-extendible by Taq DNA polymerase enzyme, and is labeled with areporter fluorescent dye and a quencher fluorescent dye. Anylaser-induced emission from the reporter dye is quenched by thequenching dye when the two dyes are located close together as they areon the probe. During the amplification reaction, the Taq DNA polymeraseenzyme cleaves the probe in a template-dependent manner. The resultantprobe fragments disassociate in solution, and signal from the releasedreporter dye is free from the quenching effect of the secondfluorophore. One molecule of reporter dye is liberated for each newmolecule synthesized, and detection of the unquenched reporter dyeprovides the basis for quantitative interpretation of the data.

TaqMan RT-PCR can be performed using commercially available equipment,such as, for example, ABI PRISM 7700 Sequence Detection System(Perkin-Elmer-Applied Biosystems, Foster City, Calif., USA), orLightcycler (Roche. Molecular Biochemicals, Mannheim, Germany). In apreferred embodiment, the 5′ nuclease procedure is run on a real-timequantitative PCR device such as the ABI PRISM 7700 Sequence DetectionSystem. The system consists of a thermocycler, laser, charge-coupleddevice (CCD), camera, and computer. The system amplifies samples in a96-well format on a thermocycler. During amplification, laser-inducedfluorescent signal is collected in real-time through fibre optics cablesfor all 96 wells, and detected at the CCD. The system includes softwarefor running the instrument and for analyzing the data.

5′ nuclease assay data are initially expressed as Ct, or the thresholdcycle. As discussed above, fluorescence values are recorded during everycycle and represent the amount of product amplified to that point in theamplification reaction. The point when the fluorescent signal is firstrecorded as statistically significant is the threshold cycle.

Real-Time Quantitative PCR (qRT-PCR)

A more recent variation of the RT-PCR technique is the real timequantitative PCR, which measures PCR product accumulation through adual-labeled fluorigenic probe (i.e., TaqMan probe). Real time PCR iscompatible both with quantitative competitive PCR and with quantitativecomparative PCR. The former uses an internal competitor for each targetsequence for normalization, while the latter uses a normalization genecontained within the sample, or a housekeeping gene for RT-PCR. Furtherdetails are provided, e.g., by Held et al., Genome Research 6: 986-994(1996).

Expression levels can be determined using fixed, paraffin-embeddedtissues as the RNA source. According to one aspect of the presentinvention, PCR primers are designed to flank intron sequences present inthe gene to be amplified. In this embodiment, the first step in theprimer/probe design is the delineation of intron sequences within thegenes. This can be done by publicly available software, such as the DNABLAT software developed by Kent, W. J., Genome Res: 12 (4): 656-64(2002), or by the BLAST software including its variations. Subsequentsteps follow well established methods of PCR primer and probe design.

In order to avoid non-specific signals, it is useful to mask repetitivesequences within the introns when designing the primers and probes. Thiscan be easily accomplished by using the Repeat Masker program availableon-line through the Baylor College of Medicine, which screens DNAsequences against a library of repetitive elements and returns a querysequence in which the repetitive elements are masked. The maskedsequences can then be used to design primer and probe sequences usingany commercially or otherwise publicly available primer/probe designpackages, such as Primer Express (Applied Biosystems); MGBassay-by-design (Applied Biosystems); Primer3 (Steve Rozen and Helen J.Skaletsky (2000) Primer3 on the VIMNV for general users and forbiologist programmers in: Krawetz 5, Misener S (eds) BioinformaticsMethods and Protocols: Methods in Molecular Biology. Humana Press,Totowa, N.J., pp 365-386).

The most important factors considered in PCR primer design includeprimer length, melting temperature (Tm), and G/C content, specificity,complementary primer sequences, and 3′ end sequence. In general, optimalPCR primers are generally 1730 bases in length, and contain about20-80%, such as, for example, about 50-60% G+C bases. Meltingtemperatures between 50 and 80° C., e.g., about 50 to 70° C., aretypically preferred. For further guidelines for PCR primer and probedesign see, e.g., Dieffenbach, C. W. et al., General Concepts for PCRPrimer Design in: PCR Primer, A Laboratory Manual, Cold Spring HarborLaboratory Press, New York, 1995, pp. 133-155; Innis and Gelfand,Optimization of PCRs in: PCR Protocols, A Guide to Methods andApplications, CRC Press, London, 1994, pp. 5-11; and Plasterer, T. N.Primerselect: Primer and probe design. Methods Mol. Biol. 70: 520-527(1997), the entire disclosures of which are hereby expresslyincorporated by reference.

Microarray Analysis

Differential expression can also be identified, or confirmed using themicroarray technique. Thus, the expression profile of GTMs can bemeasured in either fresh or paraffin-embedded tumour tissue, usingmicroarray technology. In this method, polynucleotide sequences ofinterest (including cDNAs and oligonucleotides) are plated, or arrayed,on a microchip substrate. The arrayed sequences (i.e., capture probes)are then hybridized with specific polynucleotides from cells or tissuesof interest (i.e., targets). Just as in the RT-PCR method, the source ofRNA typically is total RNA isolated from human tumours or tumour celllines, and corresponding normal tissues or cell lines. Thus RNA can beisolated from a variety of primary tumours or tumour cell lines. If thesource of RNA is a primary tumour, RNA can be extracted, for example,from frozen or archived formalin fixed paraffin-embedded (FFPE) tissuesamples and fixed (e.g., formalin-fixed) tissue samples, which areroutinely prepared and preserved in everyday clinical practice.

In a specific embodiment of the microarray technique, PCR amplifiedinserts of cDNA clones are applied to a substrate. The substrate caninclude up to 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or 75nucleotide sequences. In other aspects, the substrate can include atleast 10,000 nucleotide sequences. The microarrayed sequences,immobilized on the microchip, are suitable for hybridization understringent conditions. As other embodiments, the targets for themicroarrays can be at least 50, 100, 200, 400, 500, 1000, or 2000 basesin length; or 50-100, 100-200, 100-500, 100-1000, 100-2000, or 500-5000bases in length. As further embodiments, the capture probes for themicroarrays can be at least 10, 15, 20, 25, 50, 75, 80, or 100 bases inlength; or 10-15, 10-20, 10-25, 10-50, 10-75, 10-80, or 20-80 bases inlength.

Fluorescently labeled cDNA probes may be generated through incorporationof fluorescent nucleotides by reverse transcription of RNA extractedfrom tissues of interest. Labeled cDNA probes applied to the chiphybridize with specificity to each spot of DNA on the array. Afterstringent washing to remove non-specifically bound probes, the chip isscanned by confocal laser microscopy or by another detection method,such as a CCD camera. Quantitation of hybridization of each arrayedelement allows for assessment of corresponding mRNA abundance. With dualcolour fluorescence, separately labeled cDNA probes generated from twosources of RNA are hybridized pairwise to the array. The relativeabundance of the transcripts from the two sources corresponding to eachspecified gene is thus determined simultaneously.

The miniaturized scale of the hybridization affords a convenient andrapid evaluation of the expression pattern for large numbers of genes.Such methods have been shown to have the sensitivity required to detectrare transcripts, which are expressed at a few copies per cell, and toreproducibly detect at least approximately two-fold differences in theexpression levels (Schena et al., Proc. Natl. Acad. Sci. USA 93 (2):106-149 (1996)). Microarray analysis can be performed by commerciallyavailable equipment, following manufacturer's protocols, such as byusing the Affymetrix GenChip technology, Illumina microarray technologyor Incyte's microarray technology. The development of microarray methodsfor large-scale analysis of gene expression makes it possible to searchsystematically for molecular markers of cancer classification andoutcome prediction in a variety of tumour types.

RNA Isolation, Purification, and Amplification

General methods for mRNA extraction are well known in the art and aredisclosed in standard textbooks of molecular biology, including Ausubelet al., Current Protocols of Molecular Biology, John Wiley and Sons(1997). Methods for RNA extraction from paraffin embedded tissues aredisclosed, for example, in Rupp and Locker, Lab Invest. 56: A67 (1987),and De Sandres et al., BioTechniques 18: 42044 (1995). In particular,RNA isolation can be performed using purification kit, buffer set, andprotease from commercial manufacturers, such as Qiagen, according to themanufacturer's instructions. For example, total RNA from cells inculture can be isolated using Qiagen RNeasy mini-columns. Othercommercially available RNA isolation kits include MasterPure CompleteDNA and RNA Purification Kit (EPICENTRE (D, Madison, Wis.), and ParaffinBlock RNA Isolation Kit (Ambion, Inc.). Total RNA from tissue samplescan be isolated using RNA Stat-60 (Tel-Test). RNA prepared from tumourcan be isolated, for example, by cesium chloride density gradientcentrifugation.

The steps of a representative protocol for profiling gene expressionusing fixed, paraffin-embedded tissues as the RNA source, including mRNAisolation, purification, primer extension and amplification are given invarious published journal articles (for example: T. E. Godfrey et al. J.Molec. Diagnostics 2: 84-91 (2000); K. Specht et al., Am. J. Pathol.158: 419-29 (2001)). Briefly, a representative process starts withcutting about 10 micron thick sections of paraffin-embedded tumourtissue samples. The RNA is then extracted, and protein and DNA areremoved. After analysis of the RNA concentration, RNA repair and/oramplification steps may be included, if necessary, and RNA is reversetranscribed using gene specific promoters followed by RT-PCR. Finally,the data are analyzed to identify the best treatment option(s) availableto the patient on the basis of the characteristic gene expressionpattern identified in the tumour sample examined.

Immunohistochemistry and Proteomics

Immunohistochemistry methods are also suitable for detecting theexpression levels of the proliferation markers of the present invention.Thus, antibodies or antisera, preferably polyclonal antisera, and mostpreferably monoclonal antibodies specific for each marker, are used todetect expression. The antibodies can be detected by direct labeling ofthe antibodies themselves, for example, with radioactive labels,fluorescent labels, hapten labels such as, biotin, or an enzyme such ashorseradish peroxidase or alkaline phosphatase. Alternatively, unlabeledprimary antibody is used in conjunction with a labeled secondaryantibody, comprising antisera, polyclonal antisera or a monoclonalantibody specific for the primary antibody. Immunohistochemistryprotocols and kits are well known in the art and are commerciallyavailable.

Proteomics can be used to analyze the polypeptides present in a sample(e.g., tissue, organism, or cell culture) at a certain point of time. Inparticular, proteomic techniques can be used to assess the globalchanges of polypeptide expression in a sample (also referred to asexpression proteomics). Proteomic analysis typically includes: (1)separation of individual polypeptides in a sample by 2-D gelelectrophoresis (2-D PAGE); (2) identification of the individualpolypeptides recovered from the gel, e.g., by mass spectrometry orN-terminal sequencing, and (3) analysis of the data usingbioinformatics. Proteomics methods are valuable supplements to othermethods of gene expression profiling, and can be used, alone or incombination with other methods, to detect the products of theproliferation markers of the present invention.

Hybridization Methods Using Nucleic Acid Probes Selective for a Marker

These methods involve binding the nucleic acid probe to a support, andhybridizing under appropriate conditions with RNA or cDNA derived fromthe test sample (Sambrook, J., E Fritsch, E. and T Maniatis, MolecularCloning: A Laboratory Manual 3^(rd). Cold Spring Harbor LaboratoryPress: Cold Spring Harbor (2001)). These methods can be applied to GTMderived from a tumour tissue or fluid sample. The RNA or cDNApreparations are typically labeled with a fluorescent or radioactivemolecule to enable detection and quantification. In some applications,the hybridizing DNA can be tagged with a branched, fluorescently labeledstructure to enhance signal intensity (Nolte, F. S., Branched DNA signalamplification for direct quantitation of nucleic acid sequences inclinical specimens. Adv. Clin. Chem. 33, 201-35 (1998)). Unhybridizedlabel is removed by extensive washing in low salt solutions such as0.1×SSC, 0.5% SDS before quantifying the amount of hybridization byfluorescence detection or densitometry of gel images. The supports canbe solid, such as nylon or nitrocellulose membranes, or consist ofmicrospheres or beads that are hybridized when in liquid suspension. Toallow washing and purification, the beads may be magnetic (Haukanes, B-1and Kvam, C. Application of magnetic beads in bioassays. Bio/Technology11, 60-63 (1993)) or fluorescently-labeled to enable flow cytometry (seefor example: Spiro, A., Lowe, M. and Brown, D., A Bead-Based Method forMultiplexed Identification and Quantitation of DNA Sequences Using FlowCytometry. Appl. Env. Micro. 66, 4258-4265 (2000)).

A variation of hybridization technology is the QuantiGene Plexe assay(Genospectra, Fremont) which combines a fluorescent bead support withbranched DNA signal amplification. Still another variation onhybridization technology is the Quantikine® mRNA assay (R&D Systems,Minneapolis). Methodology is as described in the manufacturer'sinstructions. Briefly the assay uses oligonucleotide hybridizationprobes conjugated to Digoxigenin. Hybridization is detected usinganti-Digoxigenin antibodies coupled to alkaline phosphatase incolorometric assays.

Additional methods are well known in the art and need not be describedfurther herein.

Enzyme-Linked Immunological Assays (ELISA)

Briefly, in sandwich ELISA assays, a polyclonal or monoclonal antibodyagainst the GTM is bound to a solid support (Crowther, J. R. The ELISAguidebook. Humana Press: New Jersey (2000); Harlow, E. and Lane, D.,Using antibodies: a laboratory manual. Cold Spring Harbor LaboratoryPress: Cold Spring Harbor (1999)) or suspension beads. Other methods areknown in the art and need not be described herein further. Monoclonalantibodies can be hybridoma-derived or selected from phage antibodylibraries (Hust M. and Dubel S., Phage display vectors for the in vitrogeneration of human antibody fragments. Methods Mol Biol. 295:71-96(2005)). Nonspecific binding sites are blocked with non-target proteinpreparations and detergents. The capture antibody is then incubated witha preparation of sample or tissue from the patient containing the GTMantigen. The mixture is washed before the antibody/antigen complex isincubated with a second antibody that detects the target GTM. The secondantibody is typically conjugated to a fluorescent molecule or otherreporter molecule that can either be detected in an enzymatic reactionor with a third antibody conjugated to a reporter (Crowther, Id.).Alternatively, in direct ELISAs, the preparation containing the GTM canbe bound to the support or bead and the target antigen detected directlywith an antibody-reporter conjugate (Crowther, Id.).

Methods for producing monoclonal antibodies and polyclonal antisera arewell known in the art and need not be described herein further.

Immunodetection

The methods can also be used for immunodetection of marker familymembers in sera or plasma from gastric cancer patients taken before andafter surgery to remove the tumour, immunodetection of marker familymembers in patients with other cancers, including but not limited to,colorectal, pancreatic, ovarian, melanoma, liver, oesophageal, stomach,endometrial, and brain and immunodetection of marker family members inurine and stool from gastric cancer patients.

GTMs can also be detected in tissues or samples using other standardimmunodetection techniques such as immunoblotting or immunoprecipitation(Harlow, E. and Lane, D., Using antibodies: a laboratory manual. ColdSpring Harbor Laboratory Press: Cold Spring Harbor (1999)). Inimmunoblotting, protein preparations from tissue or fluid containing theGTM are electrophoresed through polyacrylamide gels under denaturing ornon-denaturing conditions. The proteins are then transferred to amembrane support such as nylon. The GTM is then reacted directly orindirectly with monoclonal or polyclonal antibodies as described forimmunohistochemistry. Alternatively, in some preparations, the proteinscan be spotted directly onto membranes without prior electrophoreticseparation. Signal can be quantified by densitometry.

In immunoprecipitation, a soluble preparation containing the GTM isincubated with a monoclonal or polyclonal antibody against the GTM. Thereaction is then incubated with inert beads made of agarose orpolyacrylamide with covalently attached protein A or protein G. Theprotein A or G beads specifically interact with the antibodies formingan immobilized complex of antibody-GTM-antigen bound to the bead.Following washing the bound GTM can be detected and quantified byimmunoblotting or ELISA.

Threshold Determination

For tests using GTM, thresholds will be derived that will enable asample to be called either positive or negative for gastric cancer.These thresholds will be determined by the analysis of cohorts ofpatients who are being investigated for the presence of gastric cancer.Thresholds may vary for different test applications; for example,thresholds for use of the test in population screening will bedetermined using cohorts of patients who are largely free of urologicalsymptoms, and these thresholds may be different to those used in testsfor patients who are under surveillance for gastric cancer recurrence. Athreshold could be selected to provide a practical level of testspecificity in the required clinical setting; that is, a specificitythat allows reasonable sensitivity without excessive numbers of patientsreceiving false positive results. This specificity may be within therange of 80-90%. An alternative method to obtain a test threshold is toplot sensitivity against specificity for different test thresholds (ROCcurves) then select the point of inflexion of the curve.

As an alternative to single thresholds, the test may use test intervalswhich provide different degrees of likelihood of presence of disease andwhich have different clinical consequences associated with them. Forexample, a test may have three intervals; one associated with a high(e.g. 90%) risk of the presence of gastric cancer, a second associatedwith a low risk of gastric cancer and a third regarded as beingsuspicious of disease. The “suspicious” interval could be associatedwith a recommendation for a repeat test in a defined period of time.

Antibodies to Gastric Cancer Markers

In additional aspects, this invention includes manufacture of antibodiesagainst GTMs. Using methods described herein, novel GTMs can beidentified using microarray and/or qRT-PCR methods. Once a putativemarker is identified, it can be produced in sufficient amount to besuitable for eliciting an immunological response. In some cases, afull-length GTM can be used, and in others, a peptide fragment of a GTMmay be sufficient as an immunogen. The immunogen can be injected into asuitable host (e.g., mouse, rabbit, etc) and if desired, an adjuvant,such as Freund's complete adjuvant or Freund's incomplete adjuvant canbe injected to increase the immune response. It can be appreciated thatmaking antibodies is routine in the immunological arts and need not bedescribed herein further. As a result, one can produce antibodies,including monoclonal or phage-display antibodies, against GTMsidentified using methods described herein.

In yet further embodiments, antibodies can be made against the proteinor the protein core of the tumour markers identified herein or againstan oligonucleotide sequence unique to a GTM. Although certain proteinscan be glycosylated, variations in the pattern of glycosylation can, incertain circumstances, lead to mis-detection of forms of GTMs that lackusual glycosylation patterns. Thus, in certain aspects of thisinvention, GTM immunogens can include deglycosylated GTM ordeglycosylated GTM fragments. Deglycosylation can be accomplished usingone or more glycosidases known in the art. Alternatively, GTM cDNA canbe expressed in glycosylation-deficient cell lines, such as prokaryoticcell lines, including E. coli and the like.

Vectors can be made having GTM-encoding oligonucleotides therein. Manysuch vectors can be based on standard vectors known in the art. Vectorscan be used to transfect a variety of cell lines to produceGTM-producing cell lines, which can be used to produce desiredquantities of GTM for development of specific antibodies or otherreagents for detection of GTMs or for standardizing developed assays forGTMs.

Kits

Based on the discoveries of this invention, several types of test kitscan be envisioned and produced. First, kits can be made that have adetection device pre-loaded with a detection molecule (or “capturereagent”). In embodiments for detection of GTM mRNA, such devices cancomprise a substrate (e.g., glass, silicon, quartz, metal, etc) on whicholigonucleotides as capture reagents that hybridize with the mRNA to bedetected is bound. In some embodiments, direct detection of mRNA can beaccomplished by hybridizing mRNA (labeled with cy3, cy5, radiolabel orother label) to the oligonucleotides on the substrate. In otherembodiments, detection of mRNA can be accomplished by first makingcomplementary DNA (cDNA) to the desired mRNA. Then, labeled cDNA can behybridized to the oligonucleotides on the substrate and detected.

Antibodies can also be used in kits as capture reagents. In someembodiment's, a substrate (e.g., a multiwell plate) can have a specificGTM capture reagent attached thereto. In some embodiments, a kit canhave a blocking reagent included. Blocking reagents can be used toreduce non-specific binding. For example, non-specific oligonucleotidebinding can be reduced using excess DNA from any convenient source thatdoes not contain GTM oligonucleotides, such as salmon sperm DNA.Non-specific antibody binding can be reduced using an excess of ablocking protein such as serum albumin. It can be appreciated thatnumerous methods for detecting oligonucleotides and proteins are knownin the art, and any strategy that can specifically detect GTM associatedmolecules can be used and be considered within the scope of thisinvention.

Antibodies can also be used when bound to s a solid support, for exampleusing an antibody chip, which would allow for the detection of multiplemarkers with a single chip.

In addition to a substrate, a test kit can comprise capture reagents(such as probes), washing solutions (e.g., SSC, other salts, buffers,detergents and the like), as well as detection moieties (e.g., cy3, cy5,radiolabels, and the like). Kits can also include instructions for useand a package.

Cancer markers can be detected in a sample using any suitable technique,and can include, but are not limited to, oligonucleotide probes, qPCR orantibodies raised against cancer markers.

It will be appreciated that the sample to be tested is not restricted toa sample of the tissue suspected of being a tumour. The marker may besecreted into the serum or other body fluid. Therefore, a sample caninclude any bodily sample, and includes biopsies, blood, serum,peritoneal washes, cerebrospinal fluid, urine and stool samples.

It will also be appreciate that the present invention is not restrictedto the detection of cancer in humans, but is suitable for the detectionof cancer in any animal, including, but not limited to dogs, cats,horses, cattle, sheep, deer, pigs and any other animal known to getcancer.

Tests for Gastric Cancer Markers in Body Fluids

In several embodiments, assays for GTM can be desirably carried out onsamples obtained from blood, plasma, serum, peritoneal fluid obtainedfor example using peritoneal washes, or other body fluids, such asurine, lymph, cerebrospinal fluid, gastric fluid or stool samples.

In general, methods for assaying for oligonucleotides, proteins andpeptides in these fluids are known in the art. Detection ofoligonucleotides can be carried out using hybridization methods such asNorthern blots, Southern blots or microarray methods, or qPCR. Methodsfor detecting proteins include such as enzyme linked immunosorbentassays (ELISA), protein chips having antibodies, suspension beadsradioimmunoassay (RIA), Western blotting and lectin binding. However,for purposes of illustration, fluid levels of a GTM can be quantifiedusing a sandwich-type enzyme-linked immunosorbent assay (ELISA). Forplasma assays, a 5 uL aliquot of a properly diluted sample or seriallydiluted standard GTM and 75 uL of peroxidaseconjugated anti-human GTMantibody are added to wells of a microtiter plate. After a 30 minuteincubation period at 30° C., the wells are washed with 0.05% Tween 20 inphosphate-buffered saline {PBS) to remove unbound antibody. Boundcomplexes of GTM and anti-GTM antibody are then incubated witho-phenylendiamine containing H₂O₂ for 15 minutes at 30° C. The reactionis stopped by adding 1 M H₂SO₄, and the absorbance at 492 nm is measuredwith a microtiter plate reader.

It can be appreciated that anti-GTM antibodies can be monoclonalantibodies or polyclonal antisera. It can also be appreciated that anyother body fluid can be suitably studied.

It is not necessary for a marker to be secreted, in a physiologicalsense, to be useful. Rather, any mechanism by which a marker protein orgene enters the serum can be effective in producing a detectable,quantifiable level of the marker. Thus, normal secretion of solubleproteins from cells, sloughing of membrane proteins from plasmamembranes, secretion of alternatively spliced forms of mRNA or proteinsexpressed therefrom, cell death (either apoptotic) can producesufficient levels of the marker to be useful.

There is increasing support for the use of serum markers as tools todiagnose and/or evaluate efficacy of therapy for a variety of cancertypes.

-   Yoshikawa et al., (Cancer Letters, 151: 81-86 (2000) describes    tissue inhibitor of matrix metalloproteinase-1 in plasma of patients    with gastric cancer.-   Rudland et al., (Cancer Research 62: 3417-3427 (2002) describes    osteopontin as a metastasis associated protein in human breast    cancer.-   Buckhaults et al, (Cancer Research 61:6996-7001 (2002) describes    certain secreted and cell surface genes expressed in colorectal    tumors.-   Kim et al., (JAMA 287(13):1671-1679 (2002) describes osteopontin as    a potential diagnostic biomarker for ovarian cancer.-   Hotte et al., (A J. American Cancer Society 95(3):507-512 (2002)    describes plasma osteopontin as a protein detectable in human body    fluids and is associated with certain malignancies.-   Martin et al, (Prostate Cancer Prostatic Dis. Mar. 9, 2004    (PMID: 15007379) (Abstract) described use of human kallikrein 2,    prostate-specific antigen (PSA) and free PSA as markers for    detection of prostate cancer.-   Hall et al (Laryngoscope 113(1):77-81 (2003) (PMID: 12679418)    (Abstract) described predictive value of serum thyroglobulin in    thyroid cancer.-   Mazzaferri et al., (J. Clin. Endocrinol. Metab.    88(4):1433-1441 (2003) (Abstract) describes thyroglobulin as a    potential monitoring method for patients with thyroid carcinoma.-   Whitley et al, (Dim Lab. Med. 24(1):29-47 (2004) (Abstract)    describes thyroglobulin as a serum marker for thyroid carcinoma.-   Kuo et al (Clin. Chim. Acta. 294(1-2):157-168 (2000) (Abstract)    describes serum matrix metalloproteinase-2 and -9 in HCP- and    HBV-infected patients.-   Koopman et al., (Cancer Epidemiol. Biomarkers Prep    13(3):487-491 (2004) (Abstract) describes osteopontin as a biomarker    for pancreatic adenocarcinoma.-   Pellegrini et al., (Cancer Immunol. Immunother. 49(7):388-394 (2000)    (Abstract) describes measurement of soluble carcinoembryonic antigen    and TIMP 1 as markers for pre-invasive colorectal cancer.-   Melle et al., (Clin. Chem. 53(4), 629-635 (2007) (Abstract)    describes HSP27 as a serum marker for pancreatic adenocarcinoma.-   Leman et al., (Urology, 69(4) 714-20 (2007) (Abstract) describes    EPCA-2 as a serum marker for prostate cancer.-   Tsigkou et al., (I Clin Endocrinol Metab, 92(7) 2526-31 (2007)    (Abstract) describes total inhibin as a potential serum marker for    ovarian cancer.-   Marchi et al., (Cancer 112, 1313-1324 (2008) (Abstract) describes    ProApolipoprotein AI as a serum marker of brain metastases in lung    cancer patients.    Methods

The following general methods were used to evaluate the suitability ofvarious approaches to molecular identification of markers associatedwith gastric tumors.

Tumor Collection

Gastric tumor samples and non-malignant gastric tissues were collectedfrom surgical specimens resected at Seoul National University Hospital.Diagnosis of gastric cancer was made on the basis of symptoms, physicalfindings and histological examination of tissues.

RNA Extraction

In some embodiments, expression of genes associated with gastric tumorswas analyzed by determining the levels of RNA in samples taken fromtumors. Frozen surgical specimens were embedded in OCT medium. 60 micronsections were sliced from the tissue blocks using a microtome,homogenized in a TriReagent:water (3:1) mix, then chloroform extracted.Total RNA was then purified from the aqueous phase using the RNeasy™procedure (Qiagen). In total, RNA from 58 gastric tumors and 58non-malignant (“normal”) gastric tissue samples were extracted and usedin the microarray analysis described below. RNA was also extracted from16 cancer cell lines and pooled to serve as a reference RNA.

Microarray Slide Preparation

Epoxy coated glass slides were obtained from MWG Biotech AG, Ebersberg,Germany) and were printed with −30,000 50mer oligonucleotides using aGene Machines microarraying robot, according to the manufacturer'sprotocol.

RNA Labeling and Hybridization

cDNA was transcribed from 10 ug total RNA using Superscript II reversetranscriptase (Invitrogen) in reactions containing 5-(3-aminoallyl)-2′deoxyuridine-5′-triphosphate. The reaction was then de-ionized in aMicrocon column before being incubated with Cy3 or Cy5 in bicarbonatebuffer for 1 hour at room temperature. Unincorporated dyes were removedusing a Qiaquick column (Qiagen) and the sample concentrated to 15 ul ina SpeedVac. Cy3 and Cy5 labeled cDNAs were then mixed with AmbionULTRAhyb buffer, denatured at 100° C. for 2 minutes and hybridized tothe microarray slides in hybridization chambers at 42° C. for 16 hours.The slides were then washed and scanned twice in an Axon 4000A scannerat two power settings to yield primary fluorescence data on geneexpression.

Normalization Procedure

To measure the expression of cancer genes in tumors and non-canceroustissues, median fluorescence intensities detected by Genepix™ softwarewere corrected by subtraction of the local background fluorescenceintensities. Spots with a background corrected intensity of less thanzero were excluded. To facilitate normalization, intensity ratios andoverall spot intensities were log-transformed. Log-transformed intensityratios were corrected for dye and spatial bias using local regressionimplemented in the LOCFIT™ package. Log-transformed intensity ratioswere regressed simultaneously with respect to overall spot intensity andlocation. The residuals of the local regression provided the correctedlog-fold changes. For quality control, ratios of each normalizedmicroarray were plotted with respect to spot intensity and localization.The plots were subsequently visually inspected for possible remainingartifacts. Additionally, an analysis of variance (ANOVA) model wasapplied for the detection of pin-tip bias. All results and parameters ofthe normalization were inserted into a Postgres-database for statisticalanalysis.

Marker Selection

Microarray gene expression data for each of 29,718 genes was rankedaccording to the relative intensity of signal for each gene in bothtumor and non-malignant tissue. Further analysis was limited to (i)genes encoding secreted proteins (ii) genes with an intensity rank intumor tissue higher than that observed for the gene (CEACAM5) encodingthe existing tumor marker CEA and (iii) genes with no significantexpression in blood or vascular tissue, as determined by EST counts inthe Unigene database (Wheeler D L et al 2003). Secreted proteins werepredicted by identifying transcripts expected to contain an N-terminalsignal peptide. Proteins with predicted transmembrane helices that werenot in the first 20 N-terminal amino acids [Krogh A. et al 2001] werediscarded. Further subcellular localization was predicted using TARGETP[Emanuelsson 0 et al 2000].

Reference numbers (MWG oligo #) for relevant oligonucleotides, and theNCBI mRNA and protein reference sequences of selected GTMs are shown inFIG. 1. FIG. 1 also shows the rank intensity of the selected GTMs inboth tumor and nonmalignant tissue. Full DNA sequences of the GTM ofthis invention are shown herein below.

Quantitative Real-Time PCR

In other embodiments, real-time, or quantitative PCR (qPCR) can be usedfor absolute or relative quantitation of PCR template copy number. Theprimer set for MUC17 (Fwd: GAGGTGGTCAGCAGCATTGAC; SEQ ID NO.1; Rev:CCTGGGAAGAGTGGTTTTTTAGC; SEQ ID NO.2) was designed using Primer ExpressV 2.0TM (Applied Biosystems) and amplified product detected using SYBRgreen labelling. ZG16 was represented by the Assay-on-Demand™ expressionassay Hs.00380609_ml (Applied Biosystems) Amplification was carried outon an ABI Prism™ 7000 sequence detection system under standard cyclingconditions.

Assays were performed over two 96 well plates with each RNA samplerepresented by a single cDNA. Up to 45 RNA samples from both gastrictumours and non-malignant gastric tissue was analysed. Each platecontained a reference cDNA standard curve, over a 625-fold concentrationrange, in duplicate. Analysis consisted of calculating the ΔCT (targetgene CT−mean reference cDNA CT). ΔCT is directly proportional to thenegative log 2 fold change. Log 2 fold changes relative to the mediannon-malignant log 2 fold change were then calculated (log 2 foldchange−median normal log 2 fold change). These fold changes were thenclustered into frequency classes and graphed.

Protein Expression and Antibody Generation

To validate ZG16 at the protein level it was necessary to generate newantibodies against the recombinant protein. The coding region 17-167 ofZG16 was PCR amplified from human cell line cDNA using the forwardprimer CACCAATGCCATTCAGGCCAGGT; SEQ ID NO.3 and the reverse primerTCAGCATCTGCTGCAGCTA; SEQ ID NO.4. The PCR product was gel purified andcloned into the “Gateway” entry vector “pENTR/dTOPO” from Invitrogenbefore being sequence to verify correct insert. Using the “Gateway”system ZG16 was then cloned from pENTR/dTOPO into the Invitrogenexpression vector pDEST17 containing an N terminal 6×HIS tag. Expressionof ZG16 was carried out in BL21-AI E. coli cells (Invitrogen), cellswere grown at 37° C. on a shaker until they were in mid log phase(OD₆₀₀=0.5) whereby they were induced at a final concentration of 0.2%arabinose and grown for a further 3 hours at 37° C. on a shaker. Cellswere harvested by centrifuging at 6000×g for 15 minutes and supernatantdiscarded. The cells were resuspended in PBS (pH7.0) and lysed bysonication using a Sonics Vibra cell at 60% power. Lysed cells werecleared by centrifuging at 12000×g for 10 minutes and the supernatantwas discarded. Cell pellet was washed three times in PBS (pH7.0) buffercontaining 0.5% Triton X-100 followed by one wash with PBS (pH7.0).Then, pellet was further washed once using 8M urea in PBS (pH7.0). Eachwash step was clarified by centrifuging at 12000×g and supernatant wasdiscarded. The pellet was then solubilised in solubilisation buffercontaining 10 mM TRIS (pH18.0), 8M urea, 100 mM NaCl overnight at roomtemperature. Solubilisation buffer was further centrifuged at 12000×g,filtered through a 0.45 nm membrane and loaded onto a NiSepharose columnpre-washed with washing buffer containing PBS (pH7.0), 8M Urea and 20 mMImidazole. After loading, column was washed with 10 column volumes ofwashing buffer and solubilised proteins were eluted in washing buffer,supplemented with 500 mM Imidazole. Eluted proteins were desalted intoPBS (pH7.0) and 8M urea buffer and then refolded by drop-wise dilutionin refolding buffer containing 50 mM Sodium Acetate (pH 4.5), 0.1MNDSB-201, 10% Glycerol, 1 mM/0.1 mM GSH/GSSH. Refolding buffer wasclarified by centrifugation at 12000×g and refolded protein wasconcentrated using Centriprep filters with nominal molecular cut-off of10 KDa (Millipore). Refolded proteins were buffer exchanged into abuffer containing 100 mM sodium acetate (pH 5.0) supplemented with 10%glycerol using a G25 desalt column and aliquots were stored at −80° C.Coomassie stained 10% SDS PAGE gel and Western blot analysiscollectively indicated the presence of a His-tagged protein of 18 KDa atup to 95% purity. The 18 KDa Coomassie stained band was excised andidentified by MALDI-TOF/TOF MS/MS to contain ZG16.

Antibodies against ZG16 were obtained by panning a phage displayantibody library with the purified ZG16 protein (Antibodies by Design; adivision of Morphosys AG, Germany).

Antibody Arrays

Antibody arrays were used to validate the candidate markers. Serumsamples were obtained from patients with gastric cancer, colorectalcancer (before and after surgery) and from surgical patients withnon-malignant disease. Samples were made available by Dunedin PublicHospital, New. Zealand, and the Christchurch Cancer Society tissue bank,Christchurch, New Zealand. Antibodies against ZG16 and MUC17 that wereobtained from either commercial sources or selected from phage libraries(Morphosys) were printed onto glass slides (Schott Nexterion Slide H)using the GeneMachines OmniGrid 100 array robot. Each array wascircumscribed with a hydrophobic pen. Slides were then washed in3×PBS-0.5% Tween 20 (3×PBS-T) before blocking with 50 mM ethanolamine in50 mM sodium borate buffer, pH8.0 followed by caseinate blocking buffer(3×PBS-T, 1% sodium caseinate). Biotin-labelled serum samples were thenadded to the slides before incubation overnight at 4° C. Slides werethen washed in 3×PBS-T before being air-dried. Bound antibody was thendetected using rolling circle amplification (RCA), largely as previouslydescribed (Haab B B, Lizardi P M. RCA-enhanced protein detection arrays.Methods Mol Biol. 2006; 328:15-29). Briefly, the slides were incubatedwith anti-biotin antibodies that had been conjugated with anoligonucleotide primer (5′-CCT GGT GCT CAA ATT TCA GTT CTG C-3′; SEQ IDNO.5). A circular DNA template was then hybridised to the slides at 37°C. for 30 mins in a humidified sealed chamber, before the slides werewashed in decreasing concentrations of PBS-T (3×PBS-0.05% Tween 20,1×PBS-0.05% Tween 20 and 0.1×PBS-0.05% Tween 20) and dried. The templatewas then extended using phi29 at 30° C. for 3 hrs before the slides werewashed and dried by centrifugation. The amplified template was thendetected using homologous fluorescently labeled probes. Slides werescanned with an Axon 4000A scanner and signal measured with the GenePixPro 6.1.0.4 software.

Cy5 fluorescence intensity was adjusted using quantile normalization,using the normalizeBetweenArrays function from the limma (Smith, 2005)package, for R (the R package for statistical computing (R DevelopmentCore). Quantile normalization adjusts the values of the intensities sothat the distribution of intensities is the same for each block (eachblock corresponding to a separate sample), by setting the quantiles ofthe intensities from different blocks to the same value. The rank ofeach intensity value does not change during this procedure, only therelative magnitude of the intensities. The assumption is that theunderlying probability distribution function describing the range ofantigen concentrations is the same for all samples. This procedureimproved the average correlation of signals between blocks across allsamples and also when considering reference-only blocks, which indicatesan improvement in the quality of the data. Genepix-flagged spots wereremoved before taking the median across replicates to obtain, normalizedintensities for each antibody.

Thus, we have identified three genes and/or proteins that are useful fordeveloping reagents, devices and kits for detecting and evaluatinggastric cancer. One or more markers of gastric cancer can be used,either singly or in combination to provide a reliable molecular test forgastric cancer.

EXAMPLES

The examples described herein are for purposes of illustratingembodiments of the invention. Other embodiments, methods and types ofanalyses are within the scope of persons of ordinary skill in themolecular diagnostic arts and need not be described in detail hereon.Other embodiments within the scope of the art are considered to be partof this invention.

Example 1 Identification of Markers for Gastric Malignancy

Markers were selected using the gene expression data obtained fromgastric tumors and non-malignant samples. The following criteria wasused for marker selection: (i) the presence of a signal sequencecharacteristic of a secreted protein (ii) the microarray signalintensity ranking in tumor tissue and (iii) the levels of correspondingESTs in blood or vascular tissues. The use of these criteria enabled theidentification of secreted markers that are abundantly expressed intumor tissue but likely to have a low background in serum, blood orplasma. FIG. 1 depicts a table that shows the three markers for gastricmalignancy selected using the above criteria, MUC5AC, MUCI7 and ZG16.FIG. 1 includes the symbol for the gene (“symbol”), the MWG oligonumber, the NCBI mRNA reference sequence number, the protein referencesequence number, the rank intensity of the gene on the arrays derivedusing tumor tissue, and the rank intensity of the gene on the arraysderived using nonmalignant tissue. All three GTMs had a higherexpression (intensity) rank than CEACAM5, the gene that encodes theexisting gastric cancer marker CEA. The lowest expressing rank possiblewas 29,718. Examination of the ranking also shows that the expression ofthese GTMs in tumor tissue was comparable to non-malignant tissue,indicating that the genes had not been strongly down-regulated duringcarcinogenesis. Unigene EST counts (Wheeler et al, 2003) for the threeGTMs in blood and vascular tissue were all zero.

Example 2 qRT-PCR Analysis

The abundance and identity of the GTMs ZG16 and MUC17 was confirmed intumor tissue using the more sensitive and accurate gene expressionquantification technique, qPCR. Up to 45 gastric tumor samples and anequal number of nonmalignant gastric tissue samples from the samepatients were analysed by RT-qPCR using the primers and probes describedin the methods section. Expression of these genes was quantified usingthe number of PCR cycles required to reach a threshold level of productamplification (Ct).

qPCR analysis confirmed the array data: both markers were readilydetected in tumor tissue by qPCR and there was no evidence for asignificant decrease in expression in tumor tissue compared tonon-malignant tissue. The abundance of these RNAs in tumor tissuecompared to non-malignant tissue is illustrated by the histograms inFIG. 2a -b.

Example 3 Detection of Gastric Tumor Marker Proteins in Serum

In certain embodiments, detection of GTM proteins can be accomplishedusing antibodies directed against either the entire protein, a fragmentof the protein (peptide) or the protein core. Methods for detecting andquantifying expression of proteins and peptides are known in the art andcan include methods relying on specific antibodies raised against theprotein or peptide. Monoclonal antibodies and polyclonal antisera can bemade using methods that are well known in the art and need not bedescribed herein further.

To detect the GTMs in serum, antibodies against the GTMs were printedonto glass slides using Gene Machine OmniGrid™ robotics. Each antibodywas repeated 8 times on the array. Serum samples from 33 gastric cancerpatients and 41 controls were then labeled with biotin before beingincubated with the antibody slides. Bound proteins were detected withanti-biotin antibodies and the signal amplified using rolling circleamplification (RCA) and fluorescent labeling. The amount of boundprotein was quantified using an Axon 4000a scanner and the Genepix6.1.0.4 software. The characteristics of the patients are shown in FIG.2.

The fluorescent signal from each antibody on the array was normalizedand the median signal for the 8 replicates expressed in arbitraryfluorescent units. Box plots illustrating the data spread are shown inFIG. 3. The median signal for MUC 17 was 18,836AU for gastric cancerpatients and 16,130 for the control group. These medians weresignificantly different (p=0.007). Significant differences between themedians were observed for two phage display ZG16 antibodies (5902 and5905) obtained from MorphoSys. The median signal for ZG16_5902 ingastric cancer patient samples was 2139AU compared to 1837AU forcontrols; the median ZG16_5905 signal in patients was 3063AU compared to1675AU for controls. The median signal between patients and controls forboth ZG16_5902 and ZG16_5905 were significantly different (p=0.05 andp=0.005, respectively).

This data demonstrates that MUC17 and ZG16 are present at significantlyhigher levels in the serum of gastric cancer patients than controls.Further differentiation between patient and control groups will beachieved by refinement of the immunological testing procedure, theidentification of antibodies with greater specificity for the targetantigens and the use of combinations of markers.

Example 8 Cells Transfected with GTM-Containing Vectors

In still further embodiments, cells are provided that can express GTMs,GTM fragments or peptide markers. Both prokaryotic and eukaryotic cellscan be so used. For example, E. coli (a prokaryotic cell) can be use toproduce large quantities of GTMs lacking in mature glycosylation (if theparticular GTM normally is glycosylated). COS cells, 293 cells and avariety of other eukaryotic cells can be used to produce GTMs that areglycosylated, or have proper folding and therefore, three-dimensionalstructure of the native form of the GTM protein. Methods fortransfecting such cells are known in the art and need not be describedfurther herein.

Example 9 Kits

Based on the discoveries of this invention, several types of test kitscan be produced. First, kits can be made that have a detection devicepre-loaded with a detection molecule (or “capture reagent”). Inembodiments for detection of GTM mRNA, such devices can comprise asubstrate (e.g., glass, silicon, quartz, metal, etc) on whicholigonucleotides as capture reagents that hybridize with the mRNA to bedetected. In some embodiments, direct detection of mRNA can beaccomplished by hybridizing mRNA (labeled with cy3, cy5, radiolabel orother label) to the oligonucleotides on the substrate. In otherembodiments, detection of mRNA can be accomplished by first makingcomplementary DNA (cDNA) to the desired mRNA. Then, labeled cDNA can behybridized to the oligonucleotides on the substrate and detected.

Regardless of the detection method employed, comparison of test GTMexpression with a standard measure of expression is desirable. Forexample, RNA expression can be standardized to total cellular DNA, toexpression of constitutively expressed RNAs (for example, ribosomal RNA)onto other relatively constant markers.

Antibodies can also be used in kits as capture reagents. In someembodiments, a substrate (e.g., a multiwell plate) can have a specificGTM capture reagent attached thereto. In some embodiments, a kit canhave a blocking reagent included. Blocking reagents can be used toreduce non-specific binding. For example, non-specific oligonucleotidebinding can be reduced using excess DNA from any convenient source thatdoes not contain GTM oligonucleotides, such as salmon sperm DNA.Non-specific antibody binding can be reduced using an excess of ablocking protein such as serum albumin. It can be appreciated thatnumerous methods for detecting oligonucleotides and proteins are knownin the art, and any strategy that can specifically detect GTM associatedmolecules can be used and be considered within the scope of thisinvention.

In embodiments relying upon antibody detection, GTM proteins or peptidescan be expressed on a per cell basis, or on the basis of total cellular,tissue, or fluid protein, fluid volume, tissue mass (weight).Additionally, GTM in serum can be expressed on the basis of a relativelyhigh-abundance serum protein such as albumin.

In addition to a substrate, a test kit can comprise capture reagents(such as probes), washing solutions (e.g., SSC, other salts, buffers,detergents and the like), as well as detection moieties (e.g., cy3, cy5,radiolabels, and the like). Kits can also include instructions for useand a package.

Although this invention is described with reference to specificembodiments thereof, it can be appreciated that other embodimentsinvolving the use of the disclosed markers can be used without departingfrom the scope of this invention.

INDUSTRIAL APPLICABILITY

Methods for detecting GTM family members include detection of nucleicacids using microarray and/or real time PCR methods and detection ofproteins and peptides. The compositions and methods of this inventionare useful in the manufacture of diagnostic devices and kits, diagnosisof disease, evaluating efficacy of therapy, and for producing reagentssuitable for measuring expression of GTM family members in biologicalsamples.

REFERENCES

-   Emanuelsson O, Nielsen H, Brunak S, von Heijne G. Predicting    subcellular localization of proteins based on their N-terminal amino    acid sequence. J Mol Biol. 2000 Jul. 21; 300(4):1005-16.-   Krogh A, Larsson B, von Heijne G, Sonnhammer E L. Predicting    transmembrane protein topology with a hidden Markov model:    application to complete genomes. J Mol Biol. 2001 Jan. 19;    305(3):567-80.-   Smyth, G. K. (2005). Limma: linear models for microarray data. In:    ‘Bioinformatics and Computational Biology Solutions using R and    Bioconductor’. R. Gentleman, V. Carey, S. Dudoit, R. Irizarry, W.    Huber (eds), Springer, New York, pages 397-420.-   R Development Core Team (2008). R: A language and environment for    statistical computing. R Foundation for Statistical Computing,    Vienna, Austria. ISBN 3-900051-07-0.-   Wheeler D L, et al. Database Resources of the National Center for    Biotechnology. Nucl Acids Res 31:28-33; 2003.

The invention claimed is:
 1. A method for detecting gastric cancer,comprising: (i) providing a sample of serum from a human being suspectedof having gastric cancer; (ii) providing samples of serum from a groupof control human beings not having gastric cancer; (iii) detecting thelevels of zymogen granule protein 16 (“ZG16”) and mucin 17 (“MUC17”) insaid sample in step (i) using rolling circle amplification; (iv)detecting the levels of a gastric cancer markers (“GTM”) zymogen granuleprotein 16 (“ZG16”) and MUC17 in said sample in step (ii) using rollingcircle amplification, and normalizing expression data; (v) normalizingexpression data obtained in step (iii) using quintile normalization; and(vi) comparing the expression of ZG16 and MUC17 in said sample in step(i) with the expression of ZG16 and MUC17 in step (ii), wherein anincrease of normalized ZG16 expression and an increase of normalizedMUC17 expression in the sample of serum from said human being comparedto the normalized expression of ZG16 and MUC17 in a group of controlsamples of serum is indicative of gastric cancer.
 2. The method of claim1, wherein said method further comprises detecting the expression levelof mucin 5AC (“MUC5AC”).
 3. The method of claim 1, wherein the one ormore further GTM family member is selected from MUC5AC, carboxypeptidaseN, polypeptide 2, 83 kDa chain (“CPN2”), matrix metalloproteinase 12(“MMP12”), inhibin (“INHBA”), insulin-like growth factor 7 (“IGFBP7”),gamma-glutamyl hydrolase (“GGH”), leucine proline enriched proteoglycan(“LEPRE1”), cystatin S (“CST4”), secreted frizzled-related protein 4(“SFRP4”), asporin (“ASPN”), cell growth regulator with EF hand domain 1(“CGREF1”), kallikrein 10 (KLK10), tissue inhibitor of metalloproteinase1 (“TIMP1”), secreted acidic cysteine-rich protein (“SPARC”),transforming growth factor, 13-induced (“TGFBI”), EGF-containingfibulin-like extracellular matrix protein 2 (“EFEMP2”), lumican (“LUM”),stannin (“SNN”), secreted phosphoprotein 1 (“SPP1”), chondroitin sulfateproteoglycan 2 (“CSPG2”), N-acylsphingosine amidohydrolase (“ASAH1”),serine protease 11 (“PRSS11”), secreted frizzled-related protein 2(“SFRP2”), phospholipase A2, group XIIB (“PLA2G12B”), spondin 2,extracellular matrix protein (“SPON2”), olfactomedin 1 (“OLFM1”),thrombospondin repeat containing 1 (“TSRC1”), thrombospondin 2(“THBS2”), adlican, cystatin SA (“CST2”), cystatin SN (“CST1”), lysyloxidase-like enzyme 2 (“LOXL2”), thyroglobulin (“TG”), transforminggrowth factor beta1 (“TGFB1”), serine or cysteine proteinase inhibitorClade H, member 1 (“SERPINH1”), serine or cysteine proteinase inhibitorClade B, member 5 (“SERPINB5”), matrix metalloproteinase 2 (“MMP2”),proprotein convertase subtilisin/kexin type 5 (“PCSK5”), hyaluronanglycoprotein link protein 4 (“HAPLN4”), CA19-9, CA72-4, pepsinogen andCEA.
 4. The method of claim 1, wherein the one or more further GTMfamily member is selected from the group consisting of cystatin SN,serpinH1 and serpinB5.
 5. The method of claim 1, wherein said step ofdetecting is carried out by detecting the levels of a GTM mRNA.
 6. Themethod of claim 1, wherein said step of detecting is carried out bydetecting the levels of a GTM cDNA.
 7. The method of claim 1, whereinsaid step of detecting is carried out using an oligonucleotidecomplementary to at least a portion of a ZG16 cDNA.
 8. The method ofclaim 1, wherein said step of detecting is carried out using qRT-PCRmethod using a forward primer and a reverse primer.
 9. The method ofclaim 1, wherein said step of detecting is carried out by detecting thelevels of a ZG16 protein or peptide.
 10. The method of claim 9 whereinsaid step of detecting is carried out using an antibody directed againstsaid ZG16.
 11. The method of claim 9, wherein said step of detecting iscarried out using a sandwich-type immunoassay method, or using anantibody chip.
 12. The method of claim 9, wherein said antibody is amonoclonal antibody.
 13. The method of claim 9, wherein said antibody isa polyclonal antiserum.